The study of the song control system of songbirds has provided fundamental insights into basic questions in neurobiology, including the neuronal basis of vocal learning and communication, the action of sex hormones on the brain and behavior, seasonal and adult neuronal plasticity, and the discovery of continued neuronal replacement in the vertebrate brain. Our long-term goal is to understand the functional organization of the song control system, and to determine how genes expressed in song control nuclei contribute to vocal learning, brain sex differentiation, and learning-related synaptic and neuronal plasticity. This goal has been greatly facilitated by the recent availability of glass-spotted microarrays containing ~18,000 unique brain-expressed cDNAs, a resource generated by an NINDS-funded collaborative consortium to study songbird neurogenomics (SoNG;NS045264). Using this resource, we have already identified ~200 genes that are enriched in the song nucleus HVC, a key nucleus involved in several aspects of song learning and production, and confirmed the patterns of expression for 20 of these using high-throughput in situ hybridization techniques. We now propose to extend this study and provide a comprehensive regional and cellular analysis of genes expressed in HVC and the songbird brain in general, and the pathways underlying molecular specializations within these nuclei. Our Specific Aims for this proposal are to: Aim 1: To identify molecular specializations of HVC in zebra finches. Aim 2: To determine the cellular expression patterns of molecular markers of HVC. Our proposed experiments represent the first steps towards generating a definitive molecular profiling of the oscine song control system and building a comprehensive, publicly available gene expression database for the zebra finch brain. We anticipate that this study will identify many novel molecular markers of specific song nuclei and uncover mechanisms involved in regulating the organization and function of the song control system of songbirds, and basic principles that control vocal learning, the basis for speech and language acquisition in humans. PUBLIC HEALTH RELEVANCE The identification of molecular markers and pathways underlying cellular specializations of specific song nuclei will likely uncover mechanisms that regulate the organization and function of the song control system of songbirds, and basic principles that control vocal learning, the basis for speech and language acquisition in humans. Our research may therefore help elucidate basic mechanisms of speech and language disorders. In a broader sense, however, our results are also likely to identify basic principles underlying brain sexual differentiation, learning and memory, and the control of brain plasticity and repair, including neuronal replacement during adulthood.